OP0183 VALIDITY OF THE EULAR RECOMMENDATIONS ON THE USE OF ULTRASOUND IN THE DIAGNOSIS OF GIANT CELL ARTERITIS
Authors: E. Fernández-Fernández, I. Monjo, D. Peiteado, A. Balsa, E. de Miguel
Journal: Annals of the Rheumatic Diseases (2022)

Background The EULAR recommendations for the use of imaging in large vessel vasculitis establish that an imaging test supported by clinical pre-test probability (PTP) is sufficient for the diagnosis of giant cell arteritis (GCA) 1 . Objectives To determine the validity of the EULAR recommendations on the use of Colour doppler ultrasound (CDUS) in GCA after calculating the PTP based on the Southend pre-test probability score (SPTPS). Methods We collected data of all patients referred to our fast-track clinic between 2016 and 2020. The SPTPS was calculated and classified as low (LR), intermediate (IR) and high risk (HR) according to the values obtained by its authors, &lt;9, 9-12 and &gt;12, respectively 2 . All patients underwent a CDUS of the temporal arteries with their common, parietal and frontal branches, and the most also axillary (86.5%), subclavian and carotid arteries. Other diagnostic tests were performed when deemed necessary by the responsible physician. TAB was performed in 34 patients (11.4%), PET-CT in 48 (16.2%) and other imaging tests such as AngioMRI or AngioCT in 8 (2.7%). The gold standard diagnosis was made according to the physician’s criteria after at least nine months of follow-up. Results Of the 297 referred patients, 97 (32.7%) were diagnosed with GCA. The SPTPS area under the ROC curve was 0.787. The LR category included 105 patients (35.4%), of which 10 (9.5%) had GCA. The IR category included 125 patients (42.1%), 40 with GCA (32%) and 85 without (68%). The HR category included 67 patients (22.5%), 47 with GCA (70.1%). In 4 of the 97 patients with GCA, the CDUS was negative and the diagnosis was confirmed with PET-CT. On the other hand, 6 of the 200 included patients without GCA (3%) had a false positive result of CDUS. There were 93 patients classified as LR with negative CDUS, and 1 of them has a final clinical diagnosis of GCA. Of the 46 patients classified as HR with positive CDUS, 1 was a false positive diagnosis of GCA. And, within the IR group, of the 84 patients with negative CDUS one had a final GCA diagnosis and of those with positive CDUS 2 were not GCA (Figure 1). Therefore, the combined use of SPTPS + CDUS only miscassified 5/297 cases (&lt;2%). Figure 1. Flow-chart of the results of the diagnostic performance of SPTPS + CDUS. Conclusion Combining the results of a pre-test probability score, such as SPTPS, and the CDUS allows for an accurate diagnosis of GCA, as established by the EULAR group, with less than 2% misclassification of diagnosis. Even a negative CDUS in patients with IR shows a strong association with a negative diagnosis. References [1]Dejaco C, Ramiro S, Duftner C, et al. EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice. Ann Rheum Dis . 2018;77(5):636-643. [2]Sebastian A, Tomelleri A, Kayani A, Prieto-Pena D, Ranasinghe C, Dasgupta B. Probability-based algorithm using ultrasound and additional tests for suspected GCA in a fast-track clinic. RMD Open . 2020;6(3). Disclosure of Interests None declared